De Wet fought in the Spanish Civil War. In the 2nd World War he worked as a secret service agent in Prague. In July 1939 both he and his wife were captured by the Gestapo, he was found guilty of treason and sentenced to death. Later he was held in solitary confinement in Brandenburg Prison, for six years.
After the war despite injuries received to his hands, he established himself as a portrait sculptor. His sitters included Ezra Pound, Brendan Behan, John Cowper Powys, Robert Graves and Edmund Blunden.